The Libre documentation is pretty clear - that finger prick testing should never be abandoned in favour of relying on the Libre (which measures interstitial fluid, not blood glucose, and runs 10-15 mins behind blood glucose measurements, and is not advised as a way of confirming blood glucose before driving).
So discrepencies between bg and libre readings are inevitable and should be expected.
My experience is that each libre sensor runs a little high or low (usually low), gets more accurate after a couple of days and becomes less inaccurate at the end of the two week lifespan. Each one also tends to be pretty consistent, so it will either run approx 0.5mmol/l high, or 1.5mmol/l low, so I allow for this.
I think that many new users of the libre approach the gadget with unrealistic expectations, and insufficient research. Lets face it, anyone who expects the libre to replace prick testing and function in the same way as a glucometer fits both of those descriptions.
I also think that there are some people whose bodies, lifestyles, expectations and immune systems are simply incompatable with the libre. Their body rejects the sensor filament, or the glue. Just as some people are intolerant to certain foods, or find certain shoe styles unwearable, or have a tendency to get a suntan in conditions that other people don't. I'm sorry that those people don't suit the libre, and I get that they find it frustrating.
As an example, I get a skin rash with almost every type of skin adhesive except the libre. When I started using the libre it was with a clear expectation that I would probably need to discontinue its use, but thought it worth the risk for a trial run. Two years on, still no reaction. For which I a truly grateful. So while I am v sympathetic to anyone who does get skin reactions to the libre glue (because I know what those reactions are like), I really hope that they never change the formulation - because if they do I may find the new formula incompatible with my body and lose the use of the libre.
Interesting. I still think that the libre documentation can be improved. Mind you, they say you should do a finger BG testing ONLY if you get from the libre an indication OR if you feel something is wrong. I had various cases where all seemed OK, yet i still opted to do a blood test and it reported a level 40% higher (see my youtubes...) I don't think that's acceptable.